Soilhttp://www.youtube.com/watch?v=qajjl3esi5E(intro sent out via kmail)

What is topsoil made of?

Topsoil Soil is the topmost portion of the

earth's crust; it supports life.

Soil is composed of minerals and organic material.

Composition is based on "parent" material (in the lower crust).

How Soil Forms Residual Soil: parent material is

bedrock beneath the soil EX: Transported Soils: soil is made from

deposits left by wind, rivers and glaciers EX:

Soil Formation

How long can take to make topsoil? (see next page)

SOIL FORMATION It can take 1,000 yrs to form topsoil. A soil forms as parent material is

weathered away. Organic material (dead plants and

animals) are mixed with weathered rock)

Soil composition Every soil is a mixture

of clay, silt, and sand Clay: Very fine/small

particle, tiny space between particles, dense

Silt: Too light, blown away (found in floodplains)

Sand: course, big spaces between particles

Soil composition Cont’d Perfect soil for plants is Loam LOAM: mixture of sand (40%), silt

(40%), and little clay (20%)

Soil Horizons (fill in) A Horizon:

B Horizon:

C Horizon:

Stalinization of soils

Build up of salts in soil—toxic for plants (can’t take up water)

Associated with excessive irrigation of water

Problem associated with poorly drained soils (CA, Colorado River Basin)

Treatment: flush soils with lots of water

Extreme cases: salt crust too thick to be flushed

Check In 1. Which zone

contains weathered parent rock?

2. Which zone contains inorganic materials that have been washed from A horizon?

3. Which zone contains microorganisms that breakdown material into nutrients?

Soil Types 11 major categories What affects soils composition? (read)

Soil Composition Parent material Plants and animals Topography---flow of water Climate

Heavy rains wash away nutrients Rainfall/high temp result in high clay

Soil is an ecosystem

BRAINSTORM: What would happen if we lost soil? How DO we loss soil?

Soil loss Erosion: soil lost by water or wind Chemical contamination Salinization Compacting by cattle hooves/machinery

40% of cropland is degraded

Stalinization of soils

Build up of salts in soil—toxic for plants (can’t take up water)

Associated with excessive water application/irriga6tion of water

Problem associated with poorly drained soils (CA, Colorado River Basin)

Treatment: flush soils with lots of water

Extreme cases: salt crust too thick to be flushed

Soil Horizons A Horizon: (topsoil)humus,

inorganic particles, microorganisms decompose organic compounds into nutrients

B Horizon: (subsoil) inorganics (iron, clay, calcium) that have been washed down into the B-horizon

C Horizon: slightly weathered parent material—rock fragments

Bedrock

Extension: Soil Scientists Some things to think about:

What do scientists do? What type of schooling do they have? Do we need soil scientists?

http://www.youtube.com/watch?v=53pNGEO08ck&feature=related

Why is soil an important resource?

Soil as a Resource Countless living organisms and

numerous species live in soil Chemical processes by these organisms

enable food to grow. Soil provides the fertility for food to

grow. Soil is a very important part of an

ecosystem

Questions?